Preparation of tetrahalomethanes



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Z,907,7 98 PREPARATION OF TETRAHALOMETHANES Robert N. Haszeldine,Cambridge, England, and Hyman Iserson, Springfield Township, MontgomeryCounty, Pa., assignors to t Pennsalt Chemicals Corporation,Philadelphia, Pa., a corporation of Pennsylvania No Drawing. ApplicationMay 7, 1957 Serial No. 657,493

Claims priority, application Great Britain October 12, 1955 12 Claims.(Cl. 260-653) This invention relates to a new method for producingtetrahalomethanes, and is a continuation-in-part of our copendingapplication Serial No. 586,901, filed May 24, 1.956, and now abandoned.

:Tetrahalornethanes are useful in a great number of industrialapplications, for example as solvents, refrigerants and fireextinguishers, to mention a few. Many of these compounds are stillrelatively expensive, however, and a general, economical process fortheir manufacture has long been sought.

. The present invention is based on the discovery that carbonyl halidescan be reacted with certain. pentahalides of group V elements having +3and +5 valences to give tetrahalomethanes in high yield. It is ofinterest that by the present invention for the first time carbonyloxygen, attached to carbon which also carries two stronglyelectro-negative groups such as halogen, can be replaced by halogen.

The general reaction may be written X MQ Z XYCQg-mZm MoQ, ..+.,.Z,.

where X and Y, Q and Z are bromine, fluorine or chlorine, where M is anelement of group V of the periodic table having +3 and-+ valences such,for example, as phosphorous, arsenic, antimony or bismuth, where n is aninteger from 0 to 5 and where m is an integer not greater than n, from 0to 2. Q is normally of less atomic weight than Z, and in such case In isnormally equal to it when n C is less than 3, and is equal to 2 when nis greater than 2.

In general the corresponding trihalide and halogen may be used in placeof the pentahalide if desired. Thus, combinations of MQ ,,Z,,, where pis from 0 to 3, may be used with Z or Q in place of MQ ,,Z,,. SO Cl mayalso be used as a halogenatiug agent in certain cases.

. Typical reactions of this general class are:

It will be understood that the above reactions merely indicate the moredesirable changes which occur. Various other reactions may also takeplace, forming other prod- The nature and proportion of these products,depends on the initial reactants and on the reaction condi l 2,907,798Patented Oct. 6, 1959 an autoclave at temperatures from about 50 C, toabout 600 C. to form dichlorodifluoromethane,monochlorotrifluoromethane, phosgene and chlorofiuorophosgene.

An appreciable quantity of CCl, is also formed, particularly attemperatures above 350 C. While the exact mechanism of the reaction hasnot been established, it is considered likely that the followingtransformations may occur:

Thus Equation 3a indicates the formation of phosgene which may thenreact with additional COF to give COFCl and finally CF CI (Equations 3band 30). At higher temperatures, and particularly above 350 C., the C001thus formed is converted to CCL, by PCl (Equation Be). The formation ofCF Cl is attributed to the fluorination of CF CI by COF (Equation 3d).

Similarly, with respect to Reaction 4, in addition to CF Cl and CCl, areobtained.

These products may be attributed to the following reactions accompanyingReaction 4:

and other reactions as in (3a) to (3e).

The reactions are, in general, conducted by placing the reactants in anautoclave and heating to a temperature between about 50 C. and about 600C. The pressure is that generated in the closed system, and is notconsidered critical. Usually it will be between about 1 and about 500atmospheres, preferably between about 1 and about 200 atmospheres. Y

The ratio of metalloid halide to carbonyl halide may vary considerablyand may range from say 0.01 to about 30 moles of metalloid halide, permole of carbonyl halide. When reaction conditions are such that themetalloid halide can be regenerated, in the manner explained below, itbecomes practicable to operate with less than 1 mole (say 0.01 to about0.8 mole) of metalloid halide, per mole of carbonyl halide. If thereaction conditions do not permit regeneration of the metalloid halide,reducing'the proportion of metalloid halide to less than thestoichiometric amount will simply result in a smaller yu'eld.

The precise temperature employed will depend on the particular reactantsinvolved. Thus, for Reactions '2 and 7 the temperature is broadlybetween 50 C. and about 600 C., usually between about 300 C. and about425 C. Reactions 3, 4, 5, 6, and 8 should be conducted between about 250C. and about 350 C. Reactions 9 to 13 are usually carried out betweenabout 50 C. and about 600 C., preferably between about C. and about 300C.

One of the outstanding advantages of the present process is that thephosphorous compound used as an initial reactant can in many cases beregenerated with relative ease. Taking, for example, the reaction carbonmonoxide in the presence of carbon to yield PO1 or with more 0001 togive PCl as described in German Patent 492,061. These reactions are208.5 grams P015.

POClx-i- COClz PCl5+ CO In Equation 15 CO+Cl may be used in place ofCOCl If desired, C1 PCl and CO may be used as the starting materials togive a cyclic process particularly suitable for industrial application,viz.

(b) POh-l- Cl: PCl

(c) CO0h+PCl CCl P001 v v C Poon+ 00 Pcn+ 009 The overall equation maybewritten larly ferric and nickel halides, such as ferric or nickelchloride.

In Equations 16 and 17 the carbon monoxide to chlorine mole ratio can bevaried from say 1:10 to :1 but is preferably about 1:1. Activated carbonmust be present in more than 100% excess, i.e. more than 1 mole ofcarbon for each mole of carbon monoxide or chlorine,

'whichever is present initially in larger amount.

The amount of phosphorous trichloride or phosphorous .pentachloride usedin Equations 16 and 17 can be varied between say 0.01 and 0.8 mole permole of carbon monoxide or chlorine, whichever of the last two compoundsis present initially in larger amount. When phosphorous trichloride isused sufiicient chlorine is added, in addition to the amount definedabove, to convert theoretically the PCl into PCl It is noteworthy, as ishereinafter shown, that with the smaller amounts of phosphorous triorpentachloride used in the process of Equations 16 and 17, carbon dioxideis produced in an arnount very nearly equivalent,

.on a. molar basis, to the amount of carbon tetrachloride produced,whereas where larger amounts of phosphorous .halides are employed littlecarbon dioxide is formed.

The fact that in Reactions 16 and 17 carbon dioxide is formed insubstantial amounts affords confirmation of the phosphorous halideregeneration reactions postulated above.

The invention will be further described in the following specificexamples.

Example I A 300 ml. stainless steel autoclave was charged with Theautoclave was evacuated and 45.7 grams COC1 was introduced in vacuo. Theautoclave was then placed in a shaking apparatus, heated to 362 C. andkept at 362, C. to 374 C. for 19.5 hours. It was then cooled and ventedto two traps in series which were cooled in liquid oxygen. When thesystem reached atmospheric pressure, it was evacuated while theautoclave was heated strongly with an open flame. The traps were thenrestored to atmospheric pressure and the products were passed through awash bottle containing aque- 'ous KOH and in series with a DryIce-acetone cooled trap. About 1.5 grams material collected in the DryIce-acetone trap. and this was discarded. The less volatile liquid whichremained in the venting traps was washed with water, dried and distilledto give 42 grams,

somewhat more than 10%.

boiling point at 73-75 C. This material was steam distilled from sodiumcarbonate solution. The lower layer in the distillate was dried andredistilled through a 6" helix-packed column to give 35.5 grams ofcarbon tetrachloride, boiling point 76" C., identified by means ofinfrared spectrum. It was free from PO1 Example II A 300 ml. stainlesssteel autoclave was charged with 50 grams (0.5 mole) COCl and 125 grams(0.6 mole) PCl in vacuo. The bomb was heated in a shaking apparatus at362372 C. for 18.5 hours. It was then vented as described in Example I.The traps were warmed up to room temperature, and volatile gases weretransferred to a vacuum apparatus and found to be equivalent to only0.0038 mole of gas. An infra-red spectrum showed that more than of thisgas consisted of COCl (ca. 1% of starting material) and about 15% COThis is equivalent to only 0.0006 mole of carbon dioxide, which showsthat this compound is not a major product. The liquid products ofboiling point greater than 20 C. were distilled through a two foothelixpacked column which was fitted with an ice water-cooled receiver.There were obtained:

(1) 80 grams, boiling point 74.2-77 C.

(2) 4 grams, boiling point 80-1045 C.

(3) More than 26 grams, boiling point 105 C.

(4) The autoclave still contained F001;, (18 grams) which was distilledat -106 C. Weight=12.5

grams.

Analysis of fraction 1 showed it to contain more than 70% C01 Thiscorresponds to a yield of at least 73%. Fraction 2 contained CCl POSIand PC13, and fractions 3 and 4 were POCl Example III A 300 ml.autoclave was charged with 100 grams (0.48 mole) PCl closed, evacuatedand cooled in liquid oxygen. Twenty-five grams COF were distilled intothe evacuated autoclave which was then heated in a shaking apparatus for16 hours at about 265 C. It was cooled to room temperature, vented toliquid nitrogen-cooled traps and was finally heated while the system wasevacuated. The product in the traps was washed three times with 15%aqueous KOH. The alkali-treated material was found to be almost puredichlorodifiuoromethane by examination of its infra-red spectrum. Theyield, based on the amount of COF taken for the reaction, was Only atrace of CF Cl was formed.

Example IV 208 grams (1 mole) ofPCl was placed in a Monel autoclavewhich was then evacuated and cooled in liquid nitrogen. 25 grams COFwere distilled into the auto clave in vacuo. The charged autoclave washeated at 330 to 350 C. for 12 hours, in a shaking apparatus, cooled andvented to traps cooled in liquid nitrogen, finally with evacuation.These traps were then vented to a Dry-Ice-ethanol-cooled trap and aliquid nitrogencooled trap connected in series. The material whichcollected in the Dry-Ice-ethanol-cooled trap was mostly phosgene withsome dichlorodifluoromethane andsome carbonyl chlorofluoride as shown byinfra-red spectroscopic' examination. The product in the liquidnitrogencooled trap contained some POF and dichlorodifluoromethane asshown by spectroscopic examination. No carbonyl fluoride Was present.The contents of these traps were washed with dilute aqueous potassiumhydroxide; the gases which did not react with the caustic were caught ina liquid nitrogen-cooled trap and found to be almost puredichlorodifluoromethane. Yield, 3.5%.

water to remove P01 and traces of phosgene, dried and 4 Example V aCarbonyl fluoride, 0.14 mole, was distilled intoa 100 ml. stainlesssteel autoclave in vacuo Phosphorous dichlorotrifluoride (0.22 mole) wasadded similarly. The autoclave was heated in a salt bath for 12 hours at300 C., cooled and then vented, finally with evacuation to a liquidoxygen-cooled trap. Spectroscopic examination of the gaseous productsrevealed the presence of C001 CF Cl and other compounds. The contents ofthe trap were then passed through 15% KOH, and the unreacted gas,examined by infra-red, consisted only of CF CI The yield of CF Cl basedon the amount of COF taken for the reaction was 1.4%.

Example VI A 300 ml. stainless steel autoclave was charged withphosphorous pentachloride (0.48 mole) and a carbonyl fluoride (0.38mole), heated at 100 for 24 hours, then cooled and vented into a seriesof cooled traps. The products were examined by infra-red spectroscopyand found to contain carbonyl chlorofluoride carbon dioxide,

dichlorodifluoromethane, chlorotn'fluoromethane, phosgene and unreactedcarbonyl fluoride and phosphorous pentachloride. The gaseous productswere washed with 20% aqueous sodium hydroxide and the washed materialfound to consist of dichlorodifluoromethane and chlorotrifluoromethane.

1 Example V11 To a 100 ml. stainless steel autoclave two-thirds full ofactive carbon pellets (Sutcliffe-Speakman 207C) mixed with animalcharcoal powder (10 grams) was added anhydrous ferric chloride (3.1grams), chlorine (2 grams), nickel carbonyl (1.5 grams) and ironcarbonyl (2.0 grams). The autoclave was heated to 400 C. for 12 hours,then cooled to room temperature and pumped out for 5 hours. Carbonmonoxide (0.20 mole), chlorine (0.25 mole), and phosphorous trichloride(0.05 mole) were added to the autoclave which was then heated to 400 C.for 9 hours. Only carbon dioxide (0.031 mole, 31%), carbon monoxide andphosgene were detected as volatile products when the autoclave wasopened at room temperature. The less volatile products were removed invacuo whilst the autoclave was heated to 350 C. during 2 hours. Afterbeing washed with dilute aqueous sodium hydroxide, the liquid productswere distilled from phosphoric anhydride to give only carbontetrachloride (0.044 mole, 44%), boiling point 75-76 C.

Example VIII What we claim is:

1. A method for making tetrahalomethanes which comprises reacting acarbonyl halide having the general formula Y where X and Y are selectedfrom the group consisting of fluorine, chlorine and bromine with areactantselected from the group consisting of pentahalides having thegeneral formula where M is a group V element having +3 and valences, Qand Z are selected from the group consisting of fluorine, chlorine andbromine, and n is a number t'rom 0" to 5;' and mixtures of a metalloidtrihalide having the general formula 3P P where is a numbenfiom 0 to 3and Q, Z and M are as defined above, and a halogen selected from thegroup consisting of Z and Q at a temperature between about 50 C. andabout 600 C., the molar ratio of said reactant to said carbonyl halidebeing between about 0.01 :1 and about 20:1, and recovering atetrahalomethane having the general formula where X, Y, Q and Z are asdefined above and m is a number from 0 to 2.

2. The method claimed in claim 1 wherein the group V element isphosphorous.

3. A method for making carbon tetrachloride which comprises reacting areactant consisting essentially of a phosphorous pentahalide containingchlorine and free from iodine, with phosgene, at a temperature betweenthe proportion of phosphorous pentachloride to carbonyl fluoride beingfrom about 0.01:1 to about 30:1.

6. A method for making chlorofluoromethanes, which comprises reactingcarbonyl fluoride with a reactant consisting essentially of phosphorousdichlorotrifiuoride, at

a temperature between about 50 C. and about 600 C.,

the proportion of phosphorous dichlorotrifluoride to carbonyl fluoridebeing between about 0.01:1 and about 30: 1.

7. A cyclic process for the production of carbon tetrachloride, whichcomprises reacting a reactant consisting essentially of phosphorouspentachloride with phosgene at a temperature between about C. and about450 C., the molar ratio of phosphorous pentachloride to phosgene beingbetween about 0.01:1 and about 30:1, to give carbon tetrachloride andphosphoryl chloride, reacting said phosphoryl chloride with carbonmonoxide to give phosphorous trichloride and reacting the phosphoroustrichloride with chlorine to regenerate phosphorous pentachloride.

8. A cyclic process for the production of carbon tetrachloride, whichcomprises reacting phosgene with a reactant consisting essentially ofphosphorous pentachloride at a temperature between about 100 C. andabout 450 C., the molar ratio of phosphorous pentachloride to phosgenebeing between about 0.01:1 and about 30:1, to give carbon tetrachlorideand phosphoryl chloride, and reacting the phosphoryl chloride withadditional phosgene to regenerate the phosphorous pentachloride.

9. A cyclic method for the production of carbon tetra- I :aaom

7C. and about 600 C., the molar ratio of P01 to phosgene being betweenabout 0.01:1 and about 30:1. T 1-1. The method claimed in claim 10wherein the ,PCl is formed in situ by the reaction of PC1 andsCl 12. Amethod for making carbon tetrachloride which comprises reacting areactant: consisting essentially of v PClzFg with phosgene at atemperature between about

1. A METHOD FOR MAKING TETRAHALOMETHANES WHICH COMPRISES REACTING ACARBONYL HALIDE HAVING THE GENERAL FORMULA